The invention relates to a method for the manufacture of glass bodies, in which method a thixotropic suspension, being the starting material for the glass body, is used to form a porous green body which is subsequently purified and sintered.
The invention further relates to arrangements for carrying out such a method as well as to the use of the glass bodies manufactured by the method in accordance with the invention.
The method mentioned in the opening paragraph is particularly suitable for the manufacture of preforms for optical waveguides.
For the manufacture of very pure quartz-glass bodies, particularly preforms for optical waveguides, methods are known in which a porous glass body known as a green body is manufactured from microdispersed SiO.sub.2 glass particles, after which the said green body is first purified in, for example, a chlorine-containing atmosphere at temperatures ranging from 600.degree. to 900.degree. C. Next, the green body is sintered at a temperature of approximately 1500.degree. C. to form compact and transparent glass the sintering temperature depends upon the size of the SiO.sub.2 particles and the homogeneity of the green body.
Processing the microdispersed quartz-glass particles involves a substantial investment in equipment (preforms for the manufacture of a green body which is easy to manipulate and presses to compact this green body) in order to obtain a green body having a density which is so high as to enable an efficient sintering process, i.e. sintering at temperatures .ltoreq.1550.degree. C. to form a glass body which is free from bubbles and reams. Such a method for the manufacture of a preform for optical waveguides is known from DE-PS No. 32 40 355, for example.
GB-PS No. 1 010 702 describes a method in which quartz-glass fibers or quartz-glass rods are manufactured by means of an extrusion moulding process. For this purpose an SiO.sub.2 suspension is brought to a gel state, which state is such that a very viscous substance is formed which can immediately be processed further in an extrusion moulding process.